Media development can be considered an art of itself. Besides medium com-
position, a major requirement for their use is sterility, meaning the absence of
microorganisms (bacteria, yeasts, fungi), which is ensured mainly by sterile filtra-
tion. Moreover, to allow optimal cell growth and virus production, media should be
buffered to provide a physiological pH value. Often a bicarbonate buffer system is
applied, where sodium bicarbonate (NaHCO3) is added to the medium, while
carbon dioxide (CO2) can be provided via the inlet air of the incubator or cultivation
vessels. Another key requirement of the medium is the adequate supply of nutrients,
such as glucose or glutamine, which are necessary for cell survival and prolifera-
tion. However, each cell type, along with the desired product, has specific com-
ponent and concentration requirements. Hence, the medium formulation needs to be
adjusted and optimized very carefully. Moreover, care should be taken during
media development to restrict the accumulation of unwanted, metabolic by-products
including ammonium and lactate. Therefore, design of experiment approaches are
frequently used to maximize the specific growth rate and virus yields. As media
TABLE 5.3
Categories of media used in animal cell culture
Abbrev.
Definition
Serum 1 Hydrolysate 2 Human-derived
components 3
Animal-derived
components 4
Peptides 5
SCM
Serum-
containing
Yes
Yes
Yes
Yes
Yes
SFM
Serum-free
No
Yes
Yes
Yes
Yes
AFM
Animal
component-
free
No
Yes
Yes
No
Yes
XFM
Xeno-free
No
Yes
Yes/No 6
No
Yes
PFM
Protein-free
No
No 7
No
No
Yes 8
CDM
Chemically
defined
No
No
Yes
Yes
Yes
Notes
1 Serum: mainly fetal bovine or fetal calf serum (FBS or FCS) from traceable sources without the risk
of prion contamination, batch-to-batch variations, human or equine sera may also be used.
2 Hydrolysate from mechanical, chemical or enzymatic treatment of soy, yeast, or animal extracts,
batch to batch variations, might still contain proteins.
3 Typically recombinant human serum albumin
4 Enzymes and/or growth factors that are not produced recombinant.
5 Protein hydrolysates.
6 Depends e.g., on cell line origin; human components may be required for a human cell line.
7 May contain hydrolysates only in special cases, then hydrolysates should be protein-free.
8 Includes amino acids or di-/tripeptides, but not polypeptides or proteins [ 36].
Yes: is allowed to be part of the medium, No: is not allowed; some suppliers differ in definition of
composition, especially regarding peptides.
96
Bioprocessing of Viral Vaccines